The present invention relates to a modular system and a method for lubricating moving components of a machine and for recovering hydraulic oil for reuse. The system and method of the present invention have particular utility in injection molding machines.
The lubrication of moving components on machinery by an automatic grease feeding system is well known in the art. Typically, these automatic greasing systems use compressed air to deliver grease through a network of piping to vital points on machinery for lubrication.
U.S. Pat. No. 2,567,147 to Cousino shows a lubricating mechanism for an injection molding machine. The lubricating mechanism is intended to add lubricant directly to the melted plastic stream to ease mold filling. This patent however lacks any disclosure of how one would lubricate the moving parts of the injection molding machine or recover hydraulic oil for recycling.
Hydraulic cylinders used in machines to operate various components typically weep hydraulic oil as they operate. As their seals wear, they tend to leak oil. Recovering this oil for reuse in the same machine is cost effective and prevents oil leakage onto the floor where it can create hazardous situations. Generally, any recovered oil must be filtered and freed from contaminants before it can be reused. Recovery of such oil typically has been performed by using drip trays beneath leaking components and a gravity drainage system to convey the oil to a sump or tank in the base of the machine. In these systems, the sump or tank must be periodically drained manually and the oil disposed of.
European Patent Application 0 831 181 to Shimada discloses a hydraulic circuit in which the internal leakage of a recycle selector valve is prevented. The hydraulic circuit includes a recycle valve attached directly to a control valve. When working fluid is returned from a rod chamber of an arm cylinder into the control valve, the recycle valve recycles a part of the working fluid through a recycle selector valve to a hydraulic supplying end. A pilot operated check valve is disposed in the oil channel that connects the rod chamber and the recycle selector valve together. When extending an arm cylinder of a hydraulic shovel, pilot pressure from the control valve shifts a pilot selector valve in such a direction as to open the pilot operated check valve. When the control valve is at the neutral position, the pilot selector valve is shifted back to the return position and closes the pilot operated check valve so that return oil of the arm cylinder is prevented from working on the recycle selector valve. This patent however does not address the problem of recovering hydraulic oil from external leakage, which oil is recovered for recycling.
A prior injection molding system developed by the assignee of the instant application collected waste oil, but lacked any means for automatically returning that oil to the main hydraulic tank for continued use. The system required someone to periodically empty the reservoir where the oil was collected. Thus, this system was not a "hands off operation" for the machine operator.
In conclusion, there is no known, commercially available system for an injection molding machine which deals with the recovery of leakage oil from hydraulic cylinders, the return of that oil to the main hydraulic tank via any route, and/or the combining of such functionality with any other system including a lubricant application system.